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Modeling of the glottal flow derivative waveform with application to speaker identification

September 1, 1999
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Journal Article
Author:
M. D. Plumpe
…
Published in:
IEEE Trans. Speech Audio Process., Vol. 7, No. 5, September 1999, pp. 569-586.
Topic:
speaker recognition
R&D area:
R&D group:

Summary

An automatic technique for estimating and modeling the glottal flow derivative source waveform from speech, and applying the model parameters to speaker identification, is presented. The estimate of the glottal flow derivative is decomposed into coarse structure, representing the general flow shape, and fine structure, comprising aspiration and other perturbations in the flow, from which model parameters are obtained. The glottal flow derivative is estimated using an inverse filter determined within a time interval of vocal-fold closure that is identified through differences in formant frequency modulation during the open and closed phases of the glottal cycle. This formant motion is predicted by Ananthapadmanabha and Fant to be a result of time-varying and nonlinear source/vocal tract coupling within a glottal cycle. The glottal flow derivative estimate is modeled using the Liljencrants-Fant model to capture its coarse structure, while the fine structure of the flow derivative is represented through energy and perturbation measures. The model parameters are used in a Gaussian mixture model speaker identification (SID) system. Both coarse- and fine-structure glottal features are shown to contain significant speaker-dependent information. For a large TIMIT database subset, averaging over male and female SID scores, the coarse-structure parameters achieve about 60% accuracy, the fine-structure parameters give about 40% accuracy, and their combination yields about 70% correct identification. Finally, in preliminary experiments on the counterpart telephone-degraded NTIMIT database, about a 5% error reduction in SID scores is obtained when source features are combined with traditional mel-cepstral measures.
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Summary

An automatic technique for estimating and modeling the glottal flow derivative source waveform from speech, and applying the model parameters to speaker identification, is presented. The estimate of the glottal flow derivative is decomposed into coarse structure, representing the general flow shape, and fine structure, comprising aspiration and other perturbations...

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Modeling of the glottal flow derivative waveform with application to speaker identification

Criteria for sprites and elves based on Schumann resonance observations

July 27, 1999
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Journal Article
Author:
Everest W. Huang
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Published in:
J. Geophys. Res., Vol. 104, No. D14, 27 July 1999, pp. 16,943-16,964.
Topic:
weather
R&D area:
R&D group:

Summary

Ground flashes with positive polarity associated with both sprites and elves excite the Earth's Schumann resonances to amplitudes several times greater than the background resonances. Theoretical predictions for dielectric breakdown in the mesosphere are tested using ELF methods to evaluate vertical charge moments of positive ground flashes. Comparisons of the measured time constants for lightning charge transfer with the electrostatic relaxation time at altitudes of nighttime sprite initiation (50-70 km) generally validate the electrostatic assumption in predictions made initially by Wilson [1925]. The measured charge moments (Q dS = 200-2000 C-km) are large in comparison with ordinary negative lightning but are generally insufficient to account for conventional air breakdown at sprite altitudes. The measured charge moments, however, are sufficient to account for electron runaway breakdown, and the long avalanche length in this mechanism also accounts for the exclusive association of sprites with ground flashes of positive polarity. The association of elves with large peak currents (50-200 kA) measured by the National Lightning Detection Network in a band pass beyond the Schumann resonance range is consistent with an electromagnetic pulse mechanism for these events.
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Summary

Ground flashes with positive polarity associated with both sprites and elves excite the Earth's Schumann resonances to amplitudes several times greater than the background resonances. Theoretical predictions for dielectric breakdown in the mesosphere are tested using ELF methods to evaluate vertical charge moments of positive ground flashes. Comparisons of the...

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Criteria for sprites and elves based on Schumann resonance observations

The FAA Terminal Convective Weather Forecast product: scale separation filter optimization

July 12, 1999
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Conference Paper
Author:
Tina J. Cartwright
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Published in:
29th Int. Conf. on Radar Meteorology, 12-16 July 1999.
Topic:
aviation weather
R&D area:
R&D group:

Summary

A large percentage of serious air traffic delay at major airports in the warm season is caused by convective weather. The FAA Convective Weather Product Development team (PDT) has developed a Terminal Convective Weather Forecast product (TCWF) that can account for short-term (out to 60 min) systematic growth and decay of thunderstorms. The team began work three years ago by evaluating air traffic user needs and requirements. We found that users were willing to trade off forecast accuracy for longer lead times, especially for air traffic management plans that were easy to implement or that incurred low risk (Forman, et al., 1999). The PDT was able to develop an operationally useful forecast product that has been demonstrated in Dallas, TX since March, 1998 (Hallowell, et al., 1999). Further improvements have been made, and testing is now taking place at both Dallas and Orlando, FL. This paper summarizes the basic algorithm methodology and presents quantitative results on optimization of the scale separation filter, which is an integral aspect of the forecast algorithm.
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Summary

A large percentage of serious air traffic delay at major airports in the warm season is caused by convective weather. The FAA Convective Weather Product Development team (PDT) has developed a Terminal Convective Weather Forecast product (TCWF) that can account for short-term (out to 60 min) systematic growth and decay...

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The FAA Terminal Convective Weather Forecast product: scale separation filter optimization

Wind shear detection using the Next Generation Airport Surveillance Radar

July 12, 1999
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Project Report
Author:
Mark E. Weber
Published in:
MIT Lincoln Laboratory Report ATC-266
Topic:
algorithms
R&D area:
R&D group:

Summary

The Federal Aviation Administration (FAA) is deploying a Weather Systems Processor (WSP) for the current-generation Airport Surveillance Radar - ASR-9. This modification exploits the coherency of the ASR-9 to perform Doppler wind measurement. Signature recognition algorithms then automatically detect low altitude wind shear phenomena, track thunderstorm motion and display appropriate graphical and alphanumeric alerts to air traffic control (ATC) personnel. The FAA and U.S. Air Force are now procuring an ASR-11 to replace older terminal surveillance radars at facilities that did not receive the ASR-9. Although the antenna pattern, scan rate and energy-on-target of the ASR-11 match the corresponding parameters of the ASR-9, two other characteristics are markedly different. It utilizes a low peak power solid state transmitter that requires transmission of long, coded waveforms and a pulse compression receiver. Secondly, its pulse transmission sequence consists of short (five-pulse) bursts at both different pulse-repetition frequencies (PRF) and different RF frequencies. In this report, we assess the technical and operational issues associated with adding a WSP to the ASR-11. The existing WSP data processing and display technology are largely re-usable for the ASR-11 based WSP. Ground clutter filter coefficients and the length and number of coherent processing intervals would need to be changed to conform to the ASR-11 pulse transmission strategy, and straightforward adaptations to the equations used in the pulse-pair weather reflectivity and Doppler velocity estimation would be required. With these changes, the ASR-11 could host the WSP, subject to performance degradations for low reflectivity wind shear phenomena such as dry microbursts and gust fronts. A benefits assessment waas performed to evaluate the operational requirements for an ASR-11 based WSP. Given that the FAA has already committed to deploy improved Low Level Wind Shear Alert Systems (LLWAS) at most ASR-11 airports, the incremental safety benefits for the ASR-11 WSP appear to be less than the cost of the equipment. A case can be made for deployment based on "situational awareness" benefits that the WSP has been demonstrated to provide to air traffic controllers. We estimate that the value to the public and airline industry of reductions in aircraft delay, and avoidance of unnecessary diversions, would be in excess of eight million dollars per year tallied across 18 of the larger ASR-11 equipped airports.
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Summary

The Federal Aviation Administration (FAA) is deploying a Weather Systems Processor (WSP) for the current-generation Airport Surveillance Radar - ASR-9. This modification exploits the coherency of the ASR-9 to perform Doppler wind measurement. Signature recognition algorithms then automatically detect low altitude wind shear phenomena, track thunderstorm motion and display appropriate...

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Wind shear detection using the Next Generation Airport Surveillance Radar

The behavior of total lightning activity in severe Florida thunderstorms

July 1, 1999
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Journal Article
Author:
Earle R. Williams
…
Published in:
Atmos. Res., Vol. 51, Nos. 3-4, July 1999, pp. 245-265.
Topic:
weather
R&D area:
R&D group:

Summary

The development of a new observational system called LISDAD (Lightning Imaging Sensor Demonstration and Display) has enabled a study of severe weather in central Florida. The total flash rates for storms verified to be severe are found to exceed 60 fpm, with some values reaching 500 fpm. Similar to earlier results for thunderstorm microbursts, the peak flash rate preceeds the severe weather at the ground by 5-20 min. A distinguishing feature of severe storms is the presence of lightning 'jumps' -- abrupt increases in flash rate in advance of the maximum rate for the storm. The systematic total lightning precursor to severe weather of all kinds -- wind, hail, tornadoes -- is interpreted in terms of the updraft that sows the seeds aloft for severe weather at the surface and simultaneously stimulates the ice microphysics that drives the intracloud lightning activity.
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Summary

The development of a new observational system called LISDAD (Lightning Imaging Sensor Demonstration and Display) has enabled a study of severe weather in central Florida. The total flash rates for storms verified to be severe are found to exceed 60 fpm, with some values reaching 500 fpm. Similar to earlier...

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The behavior of total lightning activity in severe Florida thunderstorms

Understanding-based translingual information retrieval

June 17, 1999
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Conference Paper
Author:
Young-Suk Lee
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Published in:
4th Int. Conf. on Applications of Natural Language to Information Systems, 17-19 June 1999, pp. 187-195.
Topic:
machine translation
R&D area:
R&D group:

Summary

This paper describes our preliminary research on an understanding-based translingual information retrieval system for which the input to the system is a query sentence in English, and the output of the system is a set of documents either in English or in Korean. The understanding module produces a meaning representation --- called semantic frame --- of the input sentence where the predicate-argument structure and the question-type of the input are identified, and each keyword is assigned its concept category. The translingual search module performs search on an English and Korean bilingual corpus tagged with concept categories. The results of our preliminary experiment, performed an a document set consisting of slides and notes from English and Korean briefings in a military domain, indicate that an understanding-based approach to information retrieval combined with concept-based search technique improves both precision and recall compared with a keyword match technique without understanding for both monolingual- and translingual retrieval. Current work is directed at further development of the system, and in preparation for tests on larger copora.
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Summary

This paper describes our preliminary research on an understanding-based translingual information retrieval system for which the input to the system is a query sentence in English, and the output of the system is a set of documents either in English or in Korean. The understanding module produces a meaning representation...

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Understanding-based translingual information retrieval

Demonstration of a 630-GHz photomixer used as a local oscillator

June 13, 1999
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Conference Paper
Author:
Erik K. Duerr
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Published in:
1999 IEEE MTT-S Int. Microwave Symp. Digest, Vol. 1, 13-19 June 1999, pp. 127-130.
Topic:
lasers
R&D area:
R&D group:

Summary

We report the first successful demonstration of a photomixer local oscillator (LO) integrated with a superconducting heterodyne detector. The photomixer LO generated the difference frequency of two diode lasers by optical heterodyne conversion in low-temperature-grown GaAs. The measured receiver noise temperature, 331 K at 630 GHz, compares favorably with that achieved using a varactor-multiplier LO. We also report the design of a high-power distributed photomixer structure.
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Summary

We report the first successful demonstration of a photomixer local oscillator (LO) integrated with a superconducting heterodyne detector. The photomixer LO generated the difference frequency of two diode lasers by optical heterodyne conversion in low-temperature-grown GaAs. The measured receiver noise temperature, 331 K at 630 GHz, compares favorably with that...

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Demonstration of a 630-GHz photomixer used as a local oscillator

Comparisons of long-term Schumann resonance records in Europe and North America

June 7, 1999
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Conference Paper
Author:
G. Satori
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Published in:
11th Int. Conf. on Atmos. Electr. 7-11 June 1999, pp. 705-708.
Topic:
electrical engineering
R&D area:
R&D group:

Summary

Two stations at a distance comparable with the wavelength in the Schumann resonance (SR) frequency range, one in Europe (Nagycenk, Hungary) and one in North America (West Greenwich, Rhode Island) have simultaneously monitored the natural vertical electric and horizontal magnetic field components in the frequency range of 3-25 Hz. This is a unique opportunity, as Schumann resonance stations are scarce and even fewer station have records with 5-6 year durations. The main purpose of this paper is to make comparisons in the SR time series measured simultaneously at the two field sites, thereby providing access to global behavior on the seasonal and interannual time scales. The comparative measurements described here point out distinct differences in the nature of convection in South America and in Africa, and reveal new aspects about the behavior of tropical continental convection on the ENS0 time scale.
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Summary

Two stations at a distance comparable with the wavelength in the Schumann resonance (SR) frequency range, one in Europe (Nagycenk, Hungary) and one in North America (West Greenwich, Rhode Island) have simultaneously monitored the natural vertical electric and horizontal magnetic field components in the frequency range of 3-25 Hz. This...

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Comparisons of long-term Schumann resonance records in Europe and North America

Schumann Resonances and the temporal-spatial dynamics of global thunderstorm activity

June 7, 1999
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Conference Paper
Author:
V. Mushtak
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Published in:
11th Int. Conf. on Atmospheric Electricity, 7-11 June 1999, pp. 698-700.
Topic:
weather
R&D area:
R&D group:

Summary

A two-dimensional computational ELF technique has been applied to interpret variations of peak frequencies of Schumann resosnances (SR) observed at the MIT experimental site (West Greenwich, Rhode Island). The spatial-temporal dynamics of global thunderstorm activity has been simulated on the basis of general meteorological data. It is shown that the proposed models provide a reasonable qualitative agreement between computed and observed variations for SR I to IV. Some inverse task diagrams has been constructed as an instrument for distinguishing between day-to-day thunderstorm scenarios.
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Summary

A two-dimensional computational ELF technique has been applied to interpret variations of peak frequencies of Schumann resosnances (SR) observed at the MIT experimental site (West Greenwich, Rhode Island). The spatial-temporal dynamics of global thunderstorm activity has been simulated on the basis of general meteorological data. It is shown that the...

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Schumann Resonances and the temporal-spatial dynamics of global thunderstorm activity

The relationship between the background and transient signals in Schumann resonances

June 7, 1999
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Conference Paper
Author:
Earle R. Williams
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Published in:
Proc. 11th Int. Conf. on Atmospheric Electricity, 7-11 June 1999, pp. 758-761.
Topic:
weather
R&D area:
R&D group:

Summary

Two distinct measures of the Earth's Schumann resonances -- the background and the transients -- are studied through comparisons at the mesoscale and at the continental scale. A rough proportionality is shown between the far more abundant afternoon lightning activity and the larger positive mesoscale discharges that make sprites and simultaneously ring the Earth- ionosphere cavity to levels higher than the integration of all other lightnings.
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Summary

Two distinct measures of the Earth's Schumann resonances -- the background and the transients -- are studied through comparisons at the mesoscale and at the continental scale. A rough proportionality is shown between the far more abundant afternoon lightning activity and the larger positive mesoscale discharges that make sprites and...

READ MORE
The relationship between the background and transient signals in Schumann resonances
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